What is <231>?
These methods compared the colour of a lead standard to that of the sample and reported a semi-quantitative result for the heavy metals content.
The new chapters <232> and <2232> discuss the use of more specific techniques such as Inductively Coupled Plasma (ICP), which provide quantitative results for each individual element.
For more information, check out this USP presentation.
Raw Materials
However in the current version, if chapter <231> has not been replaced, the monograph need not be tested for elemental impurities.
Please contact us if you have any concerns regarding Heavy Metals requirements in your Raw Materials.
Heavy metals or Elemental Impurities?
This is most evident with the USP’s removal of the generic heavy metals chapter <231> and a move towards specific elemental analysis.
In addition the ICH provides a detailed guideline on elemental impurities including placing them into three classes based on their toxicity and likelihood of occurrence.
For more detailed information on this check out ICH Q30.
What about the BP?
This method is essentially the same as USP <231>.
In addition the BP contains newer limit tests for Elemental Impurities such as Arsenic, Cadmium, Copper, Mercury, Nickel and Lead. These employ specific analytical techniques such as ICP-AES and ICP-MS.